Project Summary Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disease characterized by autoantibodies and an inflammatory infiltrate. BP autoantibodies recognize two hemidesmosomal proteins, BP180 and BP230. Anti-BP180 IgG autoantibodies fix complement and are pathogenic. NC16A, an extracellular domain of BP180, is the primary target of pathogenic autoantibodies. Elevated proinflammatory cytokines TNF-? and IL-1? are present in blister fluids and sera of BP patients. However, the roles of these critical inflammatory mediators and how they are up-regulated in BP remain unknown. Our preliminary results showed that subepidermal blister formation induced by pathogenic antibodies is dependent on IL-1?, a cytokine whose secretion is uniquely dependent upon the inflammasome signaling pathway. We further show that specific inflammasome mutant mice resist the pathology of BP. Therefore, the objective of this proposal is to study the role of inflammasomes in BP using our BP mouse models. Our central hypothesis for this proposal is that BP antibodies trigger an inflammasome cascade starting with the NLRP3 inflammasome (Aim 1), that activates caspase-1 and caspase-14 (Aim 3), culminating in the activation of gasdermin A, which forms the IL-1? secretion pore (Aim 2). The overall goal of this project is to increase our understanding of the innate immunity of BP and how it relates to the functions of innate immune system players in inflammation and autoimmunity. Our preliminary data are promising and strongly support our working hypothesis. Since this proposal integrates both disease mechanistic and preclinical studies, the findings are expected to have a significant impact on the treatment of patients with BP and other skin inflammatory disorders. This grant will also have broader implications to the basic biology of inflammation in the skin. Gasdermin A is a new innate immune gene known to form a pore in the cell membrane, yet its true function in vivo remains a mystery. Because IL-1? is a potent and central inflammatory mediator in skin inflammatory disease, these studies with gasdermin A will have broad impact and will reveal hitherto unimagined aspects of the basic biology of IL-1? secretion from keratinocytes.